Internal shoe drum brakes generally comprise a pair of outwardly facing arcuate, brake shoes arranged back to back and which brakes are actuated by pushing the adjacent head ends of the shoes outwardly into engagement with the drum. An anchor is positioned between the heels of the shoes in the leading and trailing shoe type brakes, while the heels of the two shoes are connected together in a duo-servo type brake. In order that a predetermined brake actuating movement will be necessary regardless of the amount of brake shoe lining wear, an expansible star wheel actuated strut is positioned between the head end of the shoes to limit their retractile movement. As shoe lining wear occurs, it is necessary to rotate the star wheel and expand the shoes outwardly by an appropriate amount to maintain the desired shoe to drum clearance. Brakes as above described have been made for many, many years, and there has been a continuing effort to reduce both the number of parts in the brake, and the cost of their manufacture. The cost of manufacture is controlled in part by the type of manufacturing process involved in making the part, and also in part by the cost of assembly, particularly where hand operations are involved.
The principal object of the present invention is the provision of a new and improved automatic adjuster having a minimum of parts, and the principal part of which is a single, stamped, adjuster lever.
Another object of the present invention is the provision of an adjuster of the above described type in which the intallation of the adjuster involves a minimum of hand labor, that is essentially limited to: picking up the adjuster lever; placing it in a forwardly inclined position against the part of the brake on which it is to be installed and with its pivot tang in the hole in which it is to be installed, and with the actuating spring loosely installed; followed by rotating the adjuster lever about its pivot to both bring its actuating abutment behind its receiving abutment and tension the actuating spring. Thereafter the adjuster lever is released to allow the actuating spring to snap the adjuster lever to its final actuating position. To applicant's knowledge, such simplicity of assembly has never been achieved heretofore.
A further object of the invention is the provision of a new and improved automatic adjuster of the above described type in which the arcuate movement of the adjuster lever is limited by the shape of the pivot tang and the shape of the hole into which it is received.
A further object of the invention is the provision of pads on the adjuster lever which limits sliding friction to appropriate portions of the brake structure.
A still further object of the invention is the provision of stamped abutment surfaces on the adjuster lever which improve the consistency of operation, and reduce sliding friction so that a minimum of spring actuating force is required for its actuation.
Further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of several embodiments described with reference to the accompanying drawings.